Multi-cylinder internal combustion engine

Abstract

To reduce the height of a crankcase by arranging a communicating passage in a proper position and to miniaturize an engine in a multi-cylinder internal combustion engine provided with an upper crankcase integrated with a cylinder block or provided separately from the cylinder block on the downside of the cylinder block and a lower crankcase connected to a lower part of the upper crankcase and provided with a communicating passage that communicates with internal spaces of plural crank chambers corresponding to plural cylinders. In the multi-cylinder internal combustion engine, a communicating hole that communicates with the communicating passage is provided on at least either side of the upper crankcase or the lower crankcase, and a cover forming the communicating passage is arranged with the cover covering the communicating hole and is attached to both crankcases across a joined plane of the upper crankcase and the lower crankcase.

What is claimed is: 
     
       1. A multi-cylinder internal combustion engine provided, on the downside of a cylinder block, with a communicating passage configured by an upper crankcase integrated with the cylinder block or provided separately from the cylinder block and a lower crankcase connected to a lower part of the upper crankcase for communicating with an internal space of a plurality of crank chambers corresponding to a plurality of cylinders, the multi-cylinder internal combustion engine comprising:
 a communicating hole that is provided at least on either side of the upper crankcase or the lower crankcase for communicating with the communicating passage; 
 a cover for forming the communicating passage, said cover being arranged with the cover covering the communicating hole; and 
 the cover is attached to both the upper and lower crankcases across a joined plane of the upper crankcase and the lower crankcase, 
 wherein a groove for arranging a sealing member is formed on a surface joined to the crankcase of the cover; and 
 each joining surface of the other upper and lower crankcases is flatly formed, 
 the communicating passage is formed in the shape of a large bowl with the communicating passage covering the communicating hole in a front view; and 
 the space for the communicating passage is configured by an inside face of the cover and the front of the crankcase, 
 wherein the communicating passage includes multiple communicating passages formed in order along the cylinder block. 
 
     
     
       2. The multi-cylinder internal combustion engine according to  claim 1 , wherein a concave portion is provided by hollowing the front of either of the upper or lower crankcase overlapped with the cover in the front view or the fronts of both the upper and lower crankcases. 
     
     
       3. The multi-cylinder internal combustion engine according to  claim 1 , wherein the cover is fixed to the upper and lower crankcases via a fastening member. 
     
     
       4. The multi-cylinder internal combustion engine according to  claim 1 , and further including a drainage hole operatively positioned within the lower crankcase, said drainage hole being in communication with an oil pan of the engine. 
     
     
       5. The multi-cylinder internal combustion engine according  claim 1 , wherein hollowing the front of either of the upper or lower crankcases increases a space for the communication passage without increasing the size and depth of the cover. 
     
     
       6. A multi-cylinder internal combustion engine wherein a communicating passage forms an internal space for a plurality of crank chambers corresponding to a plurality of cylinders to be in communication, said communicating passage being provided to a crankcase connected to the downside of a cylinder block, the multi-cylinder internal combustion engine comprising:
 an exhaust pipe being curved downwardly in front of a cylinder head and thereafter extending rearwardly; 
 wherein the communicating passage is arranged in an area enclosed by the front of the crankcase and the exhaust pipe, 
 wherein an oil filter or an oil cooler is arranged on the front of the crankcase located under the communicating passage. 
 
     
     
       7. The multi-cylinder internal combustion engine according to  claim 6 , wherein the multi-cylinder internal combustion engine is a parallel four-cylinder internal combustion engine;
 the exhaust pipe coupled to an individual exhaust port extends rearwardly via the downside of the internal combustion engine; and 
 a pair of the communicating passages in a front view are provided at the back of the adjacent exhaust pipes in a lateral direction of the internal combustion engine. 
 
     
     
       8. The multi-cylinder internal combustion engine according to  claim 6 , wherein the cylinder is inclined on the front side over the communicating passage; and
 the communicating passage is arranged in the area enclosed by the cylinder, the front of the crankcase and the exhaust pipe. 
 
     
     
       9. The multi-cylinder internal combustion engine according to  claim 8 , wherein a communicating hole connects a crank chamber and the communicating passage is arranged on the front of the crankcase; and
 the communicating hole is arranged between stud bolt insertion bosses for connecting the cylinder block and the cylinder head. 
 
     
     
       10. The multi-cylinder internal combustion engine according to  claim 8 , wherein the multi-cylinder internal combustion engine is a parallel four-cylinder internal combustion engine;
 the exhaust pipe coupled to an individual exhaust port extends rearwardly via the downside of the internal combustion engine; and 
 a pair of the communicating passages in a front view are provided at the back of the adjacent exhaust pipes in a lateral direction of the internal combustion engine. 
 
     
     
       11. The multi-cylinder internal combustion engine according to  claim 6 , wherein a communicating hole connects a crank chamber and the communicating passage is arranged on the front of the crankcase; and
 the communicating hole is arranged between stud bolt insertion bosses for connecting the cylinder block and the cylinder head. 
 
     
     
       12. The multi-cylinder internal combustion engine according to  claim 6 , wherein the cover is fixed to the upper and lower crankcases via a fastening member. 
     
     
       13. The multi-cylinder internal combustion engine according to  claim 6 , wherein a groove for arranging a sealing member is formed on a surface joined to the crankcase of the cover; and
 each joining surface of the other upper and lower crankcases is flatly formed. 
 
     
     
       14. The multi-cylinder internal combustion engine according to  claim 13 , wherein the cover is fixed to the upper and lower crankcases via a fastening member. 
     
     
       15. The multi-cylinder internal combustion engine according to  claim 13 , wherein the communicating passage is formed in the shape of a large bowl with the communicating passage covering the communicating hole in a front view; and
 the space for the communicating passage is configured by an inside face of the cover and the front of the crankcase. 
 
     
     
       16. The multi-cylinder internal combustion engine according to  claim 15 , wherein a concave portion is provided by hollowing the front of either of the upper or lower crankcase overlapped with the cover in the front view or the fronts of both the upper and lower crankcases. 
     
     
       17. The multi-cylinder internal combustion engine according to  claim 16 , wherein hollowing the front of either of the upper or lower crankcases increases a space for the communication passage without increasing the size and depth of the cover.